This invention relates to a fluid pressure indicator for providing visual indication of the magnitude of a fluid pressure condition, as of fluid, such as air, in a fluid line.
The prior art teaches various types of fluid pressure indicators, such as that of Resh U.S. Pat. No. 3,623,448, issued Nov. 30, 1971 and that of Cowan U.S. Pat. No. 3,834,346, issued Sept. 10, 1974.
The Resh patent discloses a mechanical two-position panel indicator which has a ball which is movable between two positions in which it displays either of two colors throughout the viewing area. The ball is directly positioned by a toggle overcenter spring system which is under the influence of a double acting fluidic pressure operated device. The ball will either remain in the position to which it is last moved by the overcenter system or, by an adjustment means, can be set to remain in either position except when held in the other position by the overcenter system. The Resh indicator involves complex mechanism.
The Cowan patent discloses a device for providing an indication of the condition of a pressurized fluid circuit. The device includes a closed fluid receiving chamber and a sheet of compressible material in the chamber and provided with an aperture. The sheet of compressible material is exposed to view through a clear flat lens which overlies the sheet. The device also includes fluid inlet means in open communication with the chamber. Pressurized fluid is admitted to the chamber through the fluid inlet means and the pressure of the fluid compresses the compressible material, thereby dilating the aperture and providing visual indication of the pressure of the fluid. It is stated, in effect, that the magnitude of the pressure can be judged according to the amount of dilation of the aperture. The compressible material is disclosed as an elastomeric closed cell foam material. The interior of the chamber may have a surface which contrasts in appearance with the compressible material and is visible through the dilated aperture. It has been found that the aperture does not return quickly from its fully dilated to its fully closed condition. Thus, it is possible for the device to indicate for brief periods a pressurized condition when no such condition exists. Also, the closed cell foam material can acquire a permanent set in a dilated condition. Thus, it is possible for the device to provide a permanent false indication of the existence or magnitude of pressure.
There is thus a need for a fluid pressure indicator which is of simple and inexpensive construction, with no moving mechanical parts and which will reliably display a vivid indication of the existence of fluid line pressure of at least a certain minimum magnitude.
There is also a need for a fluid pressure indicator in which the size of the displayed vivid visual indication continuously increases as the fluid line pressure increases from said certain minimum magnitude up to a certain maximum magnitude.
There is a further need for a fluid pressure indicator in which the size of the displayed vivid visual indication instantaneously and reliably changes with changes in the magnitude of the fluid pressure, over an indefinite number of cycles of operation.
There is yet an additional need for such a fluid pressure indicator in which the vivid visual indication instaneously disappears altogether when the magnitude of the fluid pressure drops below the certain minimum magnitude, over an indefinite number of cycles of operation.
There is still a further need for such a fluid pressure indicator the response of which is constant, over an indefinite number of cycles of operation.
Important objects of the present invention are to provide a fluid pressure indicator which fills all of the foregoing needs.